<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<script>
			function aaa(){
				
				var str = "我在学习JavaScript!!!!!";
				document.write(str.length+'<br/>');
				var chars = str.charAt(2);
				document.write(chars+'<br/>');
				
				var str1 = '小白,小白!!!!';
				str = str.concat(str1);
				document.write(str+'<br/>');
				
				var index= str.indexOf('!');
				document.write(index+'<br/>');
				
				var index= str.lastIndexOf('!');
				document.write(index+'<br/>');
				
				var newStr = str.replace('!!!!','****');
				document.write(newStr+'<br/>');
				
				var str2 = str.slice(2,5);
				document.write(str2+'<br/>');
				
				var str3 = '1,3,6,kk,ee,33,343';
				var arrs = str3.split(',');
				document.write(arrs[0]+'<br/>');
				
				var str4 = str3.substr(0,2);
				document.write(str4+'<br/>');
				
				var str5 = str3.substring(0,4);
				document.write(str5+'<br/>');
			  }
			
			aaa();
		</script>
	</head>
	<body>
	</body>
</html>
